1. Volume 84, Issue 2, Pages 1370-1386 (February 2003)
Stepwise Transition of the Tetra-Manganese Complex of Photosystem II to a Binuclear Mn2(μ-O)2 Complex in Response to a Temperature Jump: A Time-Resolved Structural Investigation Employing X-Ray Absorption Spectroscopy 
Pavel Pospíšil, Michael Haumann , Jens Dittmer, V. Armando Solé, Holger Dau 
Biophysical Journal 
Volume 84, Issue 2, Pages (February 2003)
DOI: /S (03)
Copyright © 2003 The Biophysical Society Terms and Conditions

2. Figure 1
Relative oxygen-evolution activity of resuspended PSII samples previously exposed to 47°C for various time periods. Oxygen evolution was measured in the presence of 5mM CaCl2 (solid circles), 5mM CaCl2 plus 50mM MgCl2 (open triangles) and 55mM CaCl2 (open circles). Additionally all media contained 15mM NaCl, 1M betaine, 20mM MES-NaOH, pH 6, and 1mM K3[Fe(CN)6] plus 0.25mM DCBQ as electron acceptors. (Solid line), Single exponential decay with a rate constant of 1min−1. (Dotted line), The small offset value discussed in the body of the text.
Biophysical Journal  , DOI: ( /S (03) )
Copyright © 2003 The Biophysical Society Terms and Conditions

3. Figure 2
Relative amplitudes of EPR signals of PSII multilayers as function of the heating time: (A), YDox and (B), hexaquo-Mn2+. The data points represent the average of the analysis of three different samples. (A) The given amplitudes of the YDox signal correspond to the height of the first low-field maximum (see inset). The solid line was calculated using a mono-exponential decay with a rate constant of 1min−1 and a small offset (dotted line). (Inset), EPR spectra of oxidized tyrosine YDox heated for the indicated time periods (in min) (EPR measurements at 20K; microwave power of 2μW; field modulation by 2.6 G at 100kHz). (B) The amplitudes of the EPR spectra due to hexaquo Mn2+ were calculated as the sum of the amplitudes of the six lines (see inset) after normalization of the whole spectra on the amplitudes of the rhombic iron signal (∼g=4, not shown). (Solid line), Calculated using the parameters listed in Table 1. (Top inset), EPR signal magnitude (solid circles) using an expanded time scale to show the sigmoidicity (lag-phase behavior) which is well reproduced by the simulations (solid line). (Bottom inset), EPR spectra of Mn2+ ligated by six water molecules (the hexaquo-Mn2+ six-line signal) at the indicated heating times. (EPR measurements at 20K; microwave power of 300μW; field modulation by 20G at 12.5kHz).
Biophysical Journal  , DOI: ( /S (03) )
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4. Figure 3
EXAFS spectra of the Mn in PSII multiplayer preparations exposed for 0min (intact PSII control, upper row) and 180min (hexaquo Mn2+-state, lower row) to 47°C. (Left column), k3-weighted EXAFS spectra in the k-space; (right column), the respective Fourier transforms. The FTs were calculated for data points ranging from 25–540 eV using an energy threshold of E0=6546 eV. Control PSII (upper row): (solid line), experimental spectrum; (dashed line), a fit with six shells of backscatterers (fit no. 8, Table 2). PSII heated for 180min (lower row): (solid line), experimental spectrum; (dashed line), a fit with a single shell of oxygen backscatterers.
Biophysical Journal  , DOI: ( /S (03) )
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5. Figure 4
A series of EXAFS spectra for PSII heated for the indicated time periods. (Left panel), k3-weighted EXAFS spectra; (right panel), the respective Fourier transforms (FT parameters as in Fig. 3). (Thin lines), Experimental spectra; (thick lines), the results of a simultaneous fit (joint-fit) of all spectra with six shells of backscatterers; (dashed lines), simulations of the spectra based on the model discussed in the text. The structural parameters used for the shown simulations are given in Table 3 and Fig. 5.
Biophysical Journal  , DOI: ( /S (03) )
Copyright © 2003 The Biophysical Society Terms and Conditions

6. Figure 5
Time dependence of the six Ni, the apparent coordination numbers per Mn atom of the Mn4-complex. The Ni (solid circle) were obtained by a least-squares joint-fit procedure of the experimental EXAFS spectra (shown in Fig. 4) with six shells of backscatterers (for the respective distances, Ri, and further details, see Table 3). The open circles represent the apparent coordination numbers obtained for an alternative three-shell simulation. The data points at each heating time represent the mean value of the coordination numbers obtained by the variations described in the legend of Table 3. The solid lines were calculated using a consecutive reaction scheme with rate constants k1, k2, and k3 of 1.0, 0.18, and 0.014min−1, respectively (see Table 1). The insets show the data points at short heating times on an expanded time scale. Note the lag phase apparent in the insets.
Biophysical Journal  , DOI: ( /S (03) )
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7. Figure 6
The mean distance between the Mn atoms separated by ∼2.7Å as function of the heating time. The distances were obtained using the joint-fit approach described in the legend of Table 3, but allowing for independent variations of RIII and 2σIII2. The line was calculated according to Eq. 4 (see also Table 1). (Inset), The Debye-Waller parameter as function of heating time.
Biophysical Journal  , DOI: ( /S (03) )
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8. Figure 7
The Mn K-edge energy as function of the heating time. The K-edge position was determined from edge spectra using the integral method of Dittmer and Dau (1998). The line was calculated using a triple exponential decay plus offset (see Table 1). The K-edge energy decreased by ∼4.5 eV after 180min of heating. (Inset), Mn K-edge spectra of PSII samples heated for 0, 1, 1.5, 2, 4, 8, 30, and 180min (from right to left; see arrow).
Biophysical Journal  , DOI: ( /S (03) )
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9. Scheme 1
Kinetic-structural model for the stepwise disassembly of the Mn complex in response to a temperature jump. Four species (or states) of Mn complexes are involved (marked by the numbers in squares); the rate constants for transitions between these species are k1, k2, and k3.
Biophysical Journal  , DOI: ( /S (03) )
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10. Scheme 2
Two alternative models for the transition from the tetranuclear Mn complex to a binuclear complex. Only bridging oxides are depicted; the presence of the bridging oxygens in parenthesis is not excluded. The Mn-Mn distances are given in Å. In the tetranuclear complex, one Mn-Mn distance of a di-μ-oxo bridged Mn pair is smaller than 2.71Å (e.g., 2.69Å), whereas the other one is greater than 2.71Å (e.g., 2.73Å). (A) Dimers-of-dimers model; (B) trimer-monomer model for the tetranuclear complex. The depicted arrangements are compatible with the electron density information obtained by protein crystallography (at 3.8-Å resolution; Zouni et al., 2001).
Biophysical Journal  , DOI: ( /S (03) )
Copyright © 2003 The Biophysical Society Terms and Conditions